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Flour Milling Lab Results

Flour Milling Lab Results

In order to fine tune my milling and sifting process, I ran a series of tests at different mill coarseness settings to see which setting might result in the best separation of bran from endosperm. I then ran a successive reduction multi-pass milling and sifting process at what appeared to be the best first pass settings and sent samples of all these tests to CII Labs to see what some of the ash content, protein content, and dough rheology might be. I also sent in some samples of Heartland Mill flours to use as a reference, since these are the types of flour I would like to emulate with my home milling process. In fact, I use Heartland Mill Hard Red Spring Wheat Berries in all these milling tests.

The equipment and general process has been described in previous blog entries on home milling and sifting.

The processing is accomplished using a Meadows 8 Inch Stone Mill and a Meadows Eccentric Sifter, as well as a sieve shaker that can stack several 12 inch diameter stainless steel or brass sieves of US standard sizes.

The CII Lab results for the initial test of varying coarseness settings of the mill have sample descriptions such as "P1 open 1/3 turn 35-50". The P1 is just a label for the setting of the mill, which is listed next. At 1/3 turn, the mill stones are separated by about 1/2 a grain width. Similarly 1/6 turn would be about 1/4 of a grain width, and so on. The numbers at the end refer to the size of the sieves used. So, a sample labeled 35-50 went through a US standard number 35 sieve and was caught in the US standard number 50 sieve.

The CII Lab results for the second test start with a first pass with a 1/6 turn opening, which seemed to be a good setting to get good initial separation of bran from endosperm in the initial tests to determine the best first pass mill coarseness setting. The sample descriptions have labels like "P2a <70" or "P1 40-80m". The P2a is the label of the pass in the process described in the process flow chart for this milling session. The "<70" refers to product that went through the US standard number 70 sieve in the stack of sieve shakers used for all but the first pass.

On the first pass, "P1", the Meadows Eccentric Sifter was used. It has sifter sections specified by the mesh size of the screens in the three sections of the sifter. So, the "40-80m" refers to flour that went through the 40 mesh section and was caught in the 80 mesh section.It so happens that due to the wire diameters of the material used in the screens, the 26m section has about the same opening size as a US standard number 20 sieve, the 40m section has about the same opening size as a US standard number 35 sieve, the 60 mesh (not used in this session) is about the same opening size as a US standard number 50 sieve, and finally the 80 mesh screen has the same opening size as a US standard number 70 sieve. So, in order to simulate the use of the Meadows sifter in subsequent passes with my smaller sieve shaker that is just more practical for these smaller amounts, I used US standard numbers 20,35,50, and 70 sieves in the stack.

I also include a spreadsheet (xls, html formats) that summarizes the results of the milling session. On the "model" sheet, there is an attempt to model what would happen at other mill settings than the one I used, based on data from the initial runs at various coarseness settings and my guesses about how the subsequent millings would go. All of that may not be very useful, except to me. However, the "model" sheet also shows a summary of the basic ash content output of each stream from the process I ran.

The flour streams with ash content around 1% had very reasonable rheological properties, which makes sense, since I was able to make some very nice breads very similar to what would have been possible with Heartland Mill Golden Buffalo flour. The stream of lower ash content flour seemed to have low mixing tolerance, so I must have inadvertently separated out some important components of proteins needed to form good quality gluten. This tells me I can create a flour with an ash content of somewhere around .85% by mixing some of the other higher protein streams with the very low ash stream to get an off-white flour that is whiter than Golden Buffalo, yet still will create a strong enough dough. I suspect that using the lowest ash stream by itself might result in a dough that doesn't have the best baking properties, since the farinograph showed weak mixing tolerance relative to the other Heartland Mill products or my own higher ash content flours more similar to Golden Buffalo.

I conducted a similar series of milling tests with Wheat Montana Bronze Chief berries, which are hard red spring wheat berries. I wanted to see if the process would go differently with the harder berries and if this would suggest changes to the process of the mill settings and sifting approach.

A flow chart of this milling session, very similar to the last, other than the addition of a fourth pass, has been posted. The preliminary report from CII Lab (now updated to final as of 3/6/08) is also posted. The nomenclature for the various passes is similar to above. However, the various tests of the "first pass" are labeled with letters. For example, a label of "PA 35-50 1/12 Turn" refers to a first pass test using a mill setting of 1/12 turn (1/3 turn is about 1/2 berry width in the separation of the stones, so 1/12 Turn would be a stone separation of about 1/8 of a berry width), and the 35-50 refers to product that fell through the #35 sieve and was caught in the #50 sieve.

The numbered passes refer to the multipass milling process in the flow chart above, which was used to create various grades of flour, bran, and red granular product.

I also include an updated version of the spreadsheet (xls, html formats) mentioned above that summarizes the results of the Wheat Montana milling session in two addition sheets ("WMactual" and "WMmodel"). On the "WMmodel" sheet, there is an attempt to model what would happen at other mill settings than the one I used, based on data from the initial runs at various coarseness settings and my guesses about how the subsequent millings would go. All of that may not be very useful, except to me. However, the "WMmodel" sheet also shows a summary of the basic ash content output of each stream from the process I ran. The "WMactual" sheet summarizes the actual results for the settings used, but it adjusts for the fact I removed some of the intermediate products to send in as samples for testing at the lab. The model is not exactly what I did, but it is a better description of what would happen if the intermediate samples had not been removed as I conducted the milling session.

Overall, what I discovered is that a finer setting on the mill seemed neccessary to get about the same breakout between "bran", "coarse red granules", "coarse white granules", and "cream flour", which is a rough way of describing 4 products that seem to be produced when I mill berries using a fairly coarse setting for the mill (1/6 turn of the screw from when the stones just touch, corresponding to about 1/4 of a grain width).

Also, I am becoming aware of the fact that there is a threshold effect in the mill setting that has a big impact on the separation of the bran and the yield of white granules that seem to then yield flour with the lowest ash content when remilled and sifted. Only the slightest change in the coarseness setting around the 1/6 turn setting for HRW or at about the 1/8 turn setting for HRS berries seems to make an enormous difference in the relative yield of "white granules" in the first pass of the mill. If the initial pass is too coarse, then result is much more bran attached to large granules, and if the setting is too fine, then the result is too much high ash content flour in the first pass, and less yield of white granules, consequently reducing any chance to extract lower ash content flour in the second milling steps.

I was also struck by the variation in protein and ash content of the berries sent in for testing. I'm wondering if there is a more accurate test or larger sample size needed for the grain in order to get more consistent results. The ash content and protein levels for the berries weren't as expected. For example, the HRS berries (Bronze Chief) from Wheat Montana should have had a higher protein content than the results on the tests show. Also, the HWS berries (Prairie Gold) had an inordinately low ash and protein content than what is normally said to prevail with this type of wheat berry. So, either the tests aren't revealing the true levels for some reason, or the wheat berries vary much more than I thought. Unfortunately, this will require convincing someone at the lab or another expert in this somewhat esoteric area to take a charitable interest in educating me.

Tempering may need to be adjusted for these berries, and I may have learned something new about the tempering time. First of all, it seemed to me that the berries milled as if they needed a little more moisture content. The amount of ash is larger overall. My sense was that the berries and the flour seemed dry. Although I added enough moisture to reach a moisture content over 14%, the moisture content tested at only 13.3%, which may have resulted from letting the berries sit for a little over 48 hours. The tempering period may have been long enough to allow some moisture to escape. Possibly these harder berries have trouble absorbing the moisture, which makes it more available to evaporate from the surface over a period of time. The lids on my tempering containers are probably not perfectly air tight, so moisture may escape very slowly over a period of time. Next time, the tempering for Wheat MT HRS and HWS berries will be conducted in two steps. First, enough moisture will be added to bring the berries to 14% moisture content. Then, in a subsequent step about 24 hours later, the berries will be tested and enough moisture will be added to bring the berries to around 14.5% moisture content followed by an additional 24 hours before milling the berries.

Comments

I need to take time to digest the results before I mill this weekend, but I really appreciate your dedication to this.

I finally got home to bake. I had 85% extraction flour from my last effort which aged about 16 days (for no other reason than I was gone and could not bake). I think there is something to this aging process as a felt (perhaps incorrectly) that the gluten development was better than my usual home grind efforts. I'll post descriptions of the process on the Milling forum along with photos and critique.

I am very curious to see how you think the aging went. I don't know if I'll want to do that, as I may decide freshness is more important, given the baking quality seems fine for the freshly milled flour. However, it would be interesting to understand this aspect of it. I noticed JMonkey had some issues with flour aged less than two full weeks. On the other hand I thought Liz had good results with 3 day aged flour. I wish I understood the rationale for using either ultra fresh or 2 week aged and nothing in between as suggested in the PR quote in JMonkey's post.

You may be the only one wanting to digest this particularly dry report. I do think it reveals some interesting things, though.

One of the most interesting was that the 1/3 turn opening didn't result in much separation. The berries seemed to break into granules, but it appeared the bran wasn't really being shredded off of the granules. Maybe it's an illusion, and what I needed was a very coarse sieve, but I don't think that was the case. It looked like the particles were just fairly large pieces of broken up berry with no real separation of bran.

The 1/6 turn setting was very different. A fair amount of fine flour came through the 80 mesh (about 225 micron opening) screen. The granules coming through the 40 mesh and caught in the 80 mesh screens (225 - 470 micron) were fairly white and proved to have an ash content of only .8% or so, compared to whole wheat flour at around 1.6%. The flour that was extracted from the granules was the lowest ash, but the baking properties might be weak, as it seemed to have questionable farinograph tolerance numbers. However, I believe that if mixed with a little of the other streams, it would be a little higher ash but probably have much better baking qualities. I suspect some important component of the gluten forming protein must be excluded from those coarse granules after the second milling and sifting.

The 1/12 turn setting was similar to 1/6, but the yield of flour coming through the 80 mesh screen on the first pass was significantly higher and lower in ash than with the 1/6 turn setting. I feel the overall result wasn't that different, but the baking quality may be better for that first pass flour, but I'll have to wait for a subsequent try at making a larger amount of flour and a multi-pass process starting with the 1/12 turn opening on the first pass. When I'll do that, I don't know, as I am more interested right now in doing all the same tests with the Wheat Montana hard spring wheat berries that are harder and higher in protein and should be require some different settings. Meanwhile, I have some traveling to do and can't even get to the Wheat Montana tests for at least another week. Also, I seem to have stopped baking and just do milling, sifting, and sending it all out for testing, which is OK for now but not a sustainable home baking lifestyle for me.

I think the aging was a good thing - I actually reduced the amount of what I do for kneading from my usual fresh home grind with superior results. There's always nutrition loss to be sure, but I have to go with conventional wisdom on this one.

I've been trying to post my photos, but seem to have reached my limits of computer competence for today. I will try later.

From what I hear, flour ground from the outer parts of the endosperm is both whiter and lower in protein quality than that ground from the part closest to the center - so perhaps you are experiencing this. I should have spent my time analysing results, but instead was trying to post - ah well! Will get back when I have really crunched the numbers...

Yes, balance. I was a knitter and decided to take up spinning so I would have better yarn. Then, of course I had less time to knit...Takes a while to reach the happy medium.

So I'm looking at the lab results and I'm trying to draw some conclusions, but I want to make sure I've got the test nomenclature correct.

It looks like you got the full test spectrum on only 2 of your own samples. The way I am currently reading things, Sample 20 corresponds to "Cream Flour FI1-516 g" on your flowchart - meaning it was the output from your first milling pass and was what exited from the 80m screen on the Meadows sifter. Sample 25 corresponds to "White Flour Fi2 - 808 g" and was what exited from the #70 sieve in the sieve shaker.

Let me know if I'm reading things correctly. We have different systems of sifting and remilling (yet, similar results) and I want to really wrap my mind around this.

Spending time analysing your results will prevent me from having to send samples out for testing myself (for a while, at least, because I feel it coming on...)

But as for understanding this aging problem there's nothing to do but get the equipment ourselves (he he he...)

The reason only two were done is that they were the only ones with big enough sample sizes for the farinograph test. I would have to do some larger runs to get farinograph tests for the other flours. The alveographs required even larger amounts, and I didn't want to go down that road immediately.

Also, note that the #70 sieve should be about equivalent in opening size to the 80 mesh sifter section on the Meadows sifter. The #35 should be equivalent to the 40 mesh sifter Meadows sifter in opening size. I used the #50 sieve also because I have a 60 mesh sifter section, which I could include in a Meadows sifting run if I wanted to. In the future, I intend to do a little bit larger amounts of flour and use the Meadows for most or all of the sifting.

I think you have correctly matched the samples with the flow chart.

There are ash and protein content on all of them, and there are some starch damage tests on some of the other flours.

One main thing that was unexpected for me, was that the lowest ash white flour coming out of the second pass had high protein and wet gluten content, yet it did not have great mixing qualities in the farinograph (low mixing tolerance). My theory is that the first grinding pass may result in some very high protein dust particles being released through the 80 mesh sieve. Maybe that extra protein in the flour out of the first pass is needed for good gluten formation and is proportionately too low in the flour from the second pass. I've been reading that some of the different types of protein vary in size and whether they adhere to the starch granules or not. I guess there are milling operations that use air separation to separate the different sized protein particles and then blends them in various flours to create desired protein specifications.

I may be inadvertently separating them and reducing the quality of the protein in the flour coming from the second pass. The other possibility is that the farinograph will not bear out in actual baking. However, that's a test I may not get to for a long time, since mostly I don't see making a bread exclusively with that low ash content flour very often, and I'm not that excited about baking a whole bread to verify that the second pass flour in fact has poor baking qualities, even if it would be interesting to verify whether the poor farinograph tolerance number results in poor baking quality in reality.

Sorry, but soon I'll be off the air for a while. I hope this helps you get what you want from those test results. It's possible I might have one more shot this evening, then I'm gone early in the morning.

Goodness! What happened with the starch damage? And why doesn't it seem to make a difference in the bread?

I promise that I will get a large enough sample to send out for test results - because we really should compare them. But I'm thinking that on some level we need to "trust the bread." Maybe the wheat berry know something that we don't, or maybe it is the ability of the baker to make small adjustments to compensate for the qualities in the flour that are less than ideal - because your bread looks great and mine is better than I've ever seen it from home milled.

I still have the malting and aging experiments to complete - but I may just need to learn to be happy to eat the bread!

So far, the tests are at odds with the baking results to some extent. The dough for the regular sourdough with the cream and golden flours mixed to what I think ought to be somewhere between .95% and 1.1% ash content had a very nice feel to it both with HRS and HRW berries each time. In spite of the questionable farinographs in the first test, and the starch damage and gluten content tests in the second, I had no problems at all with the gluten formation or the handling. The water absorption didn't seem too unusual either as far as I could tell. So, it leaves me feeling that I'm missing interpretation from an experienced flour analysis pro that might help explain some of these testing mysteries, like the high starch damage, low wet gluten content, yet reasonable farinograph tests.

I suspect some of the starch damage is real, possibly resulting from the effect of stone-milling on the harder HRS berries from Wheat MT. Their flours don't show the same amount of starch damage, but they say they are hammer milling the PG and BC flour. Still, the farinograph comes out fine and doesn't show unusual water absorption.

The gluten content tests seem off to me. I don't see how the flours could perform well in the farinograph or in my baking usage with so little gluten, and why would the gluten be so different between my flours and the Wheat MT flours themselves? I'm guessing there is something going on, like the development of the gluten is somehow not happening before they start washing away the rest of the material in the test or some other explanation like that. Maybe there is some difference in the flour behavior affecting the gluten content test that I don't run into making the bread itself and that doesn't cause a problem with the farinograph.

I don't know if I'm doing anything special to handle the flour. The only thing I do that's maybe a little unusual is the long overnight soak in the refrigerator I almost always do. This is a process I discovered helps a lot for whole grain flours and breads, and I tried it with HM Golden Buffalo, thinking it was akin to whole grain flour. It worked well, so I've continued to use the technique in these breads.

Other than that, I stick to very standard Hamelman style advice, i.e. not too aggressive with early mixing, more folding later. I also find that getting the water just right can make a big difference. In this case, the water was higher than I usually like, so the bread came out more ciabatta-like. It's beautiful in a way, but it leaks butter, honey, or whatever else like a sieve. Next time, I will probably go lower in hydration to get a smaller hole structure and a little more density, as nice as this bread turned out.

The WW mash bread is a real winner for spreading with some tahini and honey, a big favorite. It's a bit of a calorie explosion, but a little of that mash bread with tahini and honey and a couple of good capuccinos, and I'm in a good mood for hours. I have to try adding yeast to the final dough, as PR suggests, to see if I can get it just a touch less dense. It's very good as is, even if a touch dense, but if I could raise just 20-30% more without losing too much of the flavor, it would be all for the better.

I agree - we're missing something here. Now that you mention it - yes, those gluten numbers don't match with the results you get. But the absorption numbers are a bit high - which squares with the starch damage.

I don't know - I'm at the point where I need to really dig into the science or just step back and bake for awhile.

You nailed my general thought process when I look at the ciabatta style loaves. What happens to the butter? - is my thought. (I house churn a tasty cultured butter - so it is important that it not fall through the bread.) But they are lovely.

Since my milling output is fairly small and I do want to try the malt experiment, it may be awhile until I return to any other type of bread than test loaves. I really try to do those by the numbers so I'm trying to vary only one thing at a time. A little boring, but useful nonetheless.

I've really never encountered this practice of soaking the flour before. I must confess that I don't have Mr. Reinhart's latest book - does he go into the method in there? Sounds like I should do a control test on that - but here's a question. I've become a pretty devoted adherent to the "desired dough temperature" formula. If I add all of my remaining water to the flour and let it soak overnight - how do I get the desired dough temperature? Or do you just let it go? Do you think there would be an issue with putting the soaking flour into my proofing box (litterally, a box, with a heating pad which stays at about 72 degrees)?

And I've still got that flour waiting for the 2 month mark - so I can test aging...

Good luck with adding yeast to your mash bread. I'll be honest, after handling levain for so long, I just can't seem to keep up with commercial yeast anymore. On the rare occasions that I use it (I've even made levain croissants, if you can get your mind around that) the bread seems to rise at a run. You might want to try half the recommended amount of yeast so that you still get a relatively slow rise.

JMonkey first got me trying soaking flour overnight, which was advice I picked up from his discussion of some of the things he felt helped whole grain bread. PR also mentions soakers in his book when discussing softening bran and enzyme activity. When I tried it with whole grain flours, it was the first time I got a decently light whole grain bread, so I've stuck with the technique for whole grains. Later on, as I got in touch with the idea that flours like HM-GB and my own high ash content flours were close cousins of whole grain flour, I decided to try soaking them, and it seemed to work well.

I have rise time models built into my recipe spreadsheets, so I can take the temperature of the dough as fermentation progresses and get estimates from my model of the right time to shape and the right time to bake. So, I'll try to manage the dough temperature by placing my dough in a warm or cool spot depending on what I'm trying to accomplish, but regardless of that, taking the temperature every hour or two and entering that into my spreadsheet gives me a very good idea when the dough has fermented enough for shaping or baking. Also, I model out the timing ahead of time knowing that I may be starting with cool dough at around 60F at the end of my mixing because of mixing refrigerated soakers and warm levains in the DLX for a few minutes or whatever the process is. It helps a lot because then I also have a brick oven to fire and have ready at the right time. I suspect that if you soak all night at 72F, the problem might be that it'll result in too much enzyme activity, but who knows without trying. I could easily imagine that two or three hours soaking at 72F would be equivalent to all night in the refrigerator.

I would only add a small amount of yeast to the mash bread, most likely. Something like 1/4-1/2 tsp in 2Kg of flour added to the final dough is probably what I would do. Since some amount of the flavor is really just coming from the mash, it might make for a lighter bread without changing the flavor that much.

So much to try - so little time...Well, I 'm charting out my test bake schedule and the malt or no malt seems to go first. But I want to try the soaked flour idea and now that I think of it, I can just bring the whole thing up to temperature by heating it prior to baking.

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